As of today Google requires the items below.
The below list will give you an idea of what clients must make sure they have before submitting:
Availability
Product Name
Product Category
Description
Image (at least 400px X 400px)
Product Condition
Price (with default currency for country being listed)
GPS Enabled set to Y.
GPS Category set to a valid BigCommerce category.
Category Mapped to GPS
Unique Identifier Requirement for Google Product Search:
Media – Must have either UPC or GTIN on BigCommerce (for now I would not use both).
Books – Must have the ISBN number entered into the GTIN field on BigCommerce.
Apparel – Must have a Brand, Color, Size, Age Group, Gender. Material and Pattern are required if applicable.
Custom Made Goods – No Identifiers required for now.
All Other Goods – Must have at least two of the following three:
Brand
UPC or GTIN (not a good idea to have both right now)
MPN